postfix errors

Not sure if this is the result of a recent upgrade but as of 4 days ago, mail has stopped flowing. We have postfix configured to send mail only, which has been working flawlessly. No modifications to config, but mail is in queue and cannot be delivered.
Error in log is "warning: mysql:/etc/postfix/mysql-virtual_outgoing_bcc.cf is unavailable. open /etc/postfix/mysql-virtual_outgoing_bcc.cf: Permission denied"
The permissions on the file appear to be 600 for rootostfix.
Any recommendations/suggestions?

Thanks you for the quick reply. There are messages stuck in queue, generated from contact forms on web pages. Any clues as to what may have changed permissions? As mentioned, we have not actively modified permissions. It appears most of the MySQL*.cf files are set to 640 with only outgoing_bcc.cf, greylist.cf, and login_maps.cf set to 600. Should all be set to 640?